Peristaltic pumps are used in a variety of applications in which it is desirable to convey fluid in accurately controllable quantities. Peristaltic pumps typically include a rotary portion that compels the movement of a fluid by peristaltic compression of resilient tubing containing the fluid.
Imaging systems using inkjet printing have become widely known, and are often implemented using thermal inkjet technology. Such technology forms characters and images on a medium, such as paper, by expelling droplets of ink in a controlled fashion so that the droplets land on the medium. The printer, itself, can be conceptualized as a mechanism for moving and placing the medium in a position such that the ink droplets can be placed on the medium, a printing cartridge which controls the flow of ink and expels droplets of ink to the medium, and appropriate hardware and software to position the medium and expel droplets so that a desired graphic is formed on the medium. A conventional print cartridge for an inkjet type printer comprises an ink containment device and an ink-expelling apparatus, commonly known as a printhead, which heats and expels ink droplets in a controlled fashion.
In some inkjet type printers, a peristaltic pump head is used to drive multiple, resilient tubes to convey ink between the containment device and the printhead. Unless the resilient tubes are perfectly aligned parallel to the occlusion of the pump roller, the tubes have a tendency to migrate to a point of lower force during pump operation. Tube migration can result in the tubes bunching together, which can increase the force required to collapse the tubes. The forces applied by bunched tubes can also change the natural restoring force of the tubes. Tube migration can also result in individual tubes moving to one side of the pump or the other, which can also undesirably alter the pumping forces exerted on the tubes.
A variety of approaches to pump design have been presented in an attempt to reduce tube migration. In one example, pumps have been developed in which each tube is located in a separate drive head. While this reduces the likelihood of tube migration, it is comparatively expensive, requiring redundant parts and additional assembly time.
In another approach, the tubes are stretched over respective rollers in such a way as to maintain the tubes under constant tension. This approach is usually used in conjunction with additional mechanisms to maintain precise parallelism between the rollers and the occlusion. Again, although this approach reduces the likelihood of tube migration, it is also comparatively expensive, often requiring additional parts, control systems, and assembly time.
It can be seen from the foregoing that the need exists for a simple, inexpensive, arrangement for securing tubes in peristaltic pumps.